From the Research
The normal AC joint space should be between 1.1 to 3.5 millimeters wide in men and 0.9 to 3.1 millimeters wide in women, as a joint space wider than 7 mm in men and 6 mm in women is abnormal. This measurement represents the distance between the lateral end of the clavicle and the acromion process of the scapula. A space narrower than these values may indicate joint degeneration or arthritis, while a space wider than these values often suggests AC joint separation or instability. The AC joint space is best evaluated on standardized radiographs, particularly with the patient in an upright position and with both shoulders visible for comparison 1.
Key Points to Consider
- The joint space may appear different depending on patient positioning and radiographic technique, so comparison with the contralateral side is helpful for accurate assessment.
- This space is maintained by the integrity of the acromioclavicular and coracoclavicular ligaments, which provide stability to the joint.
- Age-related changes can naturally decrease this space over time, so clinical correlation with symptoms is important when evaluating AC joint pathology.
- A study from 1983 found that the joint space was significantly wider in men and that there was a highly significant reduction of the joint space with age in both men and women 1.
- Other studies have also highlighted the importance of considering normal variation in the alignment of the acromioclavicular joint when making a diagnosis 2, 3, 4.
Clinical Implications
- When evaluating AC joint pathology, it is essential to consider the patient's symptoms, medical history, and radiographic findings to make an accurate diagnosis.
- A thorough understanding of the anatomy and common pathologies of the acromioclavicular joint is crucial for providing effective treatment and management options.
- The AC joint space should be evaluated in the context of the patient's overall clinical presentation, rather than relying solely on radiographic measurements.